Mating-dependent plasticity of the olfactory system in an insect.

4. ANTON S, BARROZO RB, JARRIAULT D, GADENNE C.

Congreso; XIX European Chemoreception Research Organization (ECRO); 2009

In many animals including insects, reproduction involves detection and central processing of relevant chemical cues that lead to appropriate behaviors. Sex pheromones are generally considered as attractants and play a key role in the encountering of sexual partners, ultimately leading to copulation. In the contrary to females, for which mating induces drastic behavioral and physiological changes, males can often remate after a variable time delay. However, males are limited with respect to the number of ejaculates they can deliver and the time required to restore depleted reserves and should. In the moth, Agrotis ipsilon, males cease to respond to the female-produced sex pheromone after mating. This plasticity is not only seen at the behavioural level, but is accompanied by a change in the sensitivity of central olfactory neurons1. The loss of sensitivity after mating is restored during the next day. This transient neuronal plasticity serves as an energy-saving strategy by switching off the olfactory system and therefore preventing males from mating unsuccessfully. We investigated the neurobiological mechanisms underlying this mating-induced change in behaviour. Extracellular recordings from antennal receptor neurons revealed no differences in responses to the sex pheromone between virgin and mated males. Detailed analysis of intracellularly recorded responses in the antennal lobe (the primary olfactory centre of insects), revealed however clear differences not only in the response threshold to pheromone, but also in other measured parameters such as spike frequency and latency of the responses between virgin and mated males. These physiological changes were restricted to responses to sex pheromone, but were not observed for responses to general odours, such as plant volatiles. In addition we could show that biogenic amines such as octopamine play a role in the mating-induced plasticity of pheromone sensitivity, by using molecular and pharmacological approaches. 1. Gadenne et al 2001. Proc R. Soc. London B. 268:1631-5